The invention relates to a device for mounting at least one pair of brush holders with brushes located diametrically opposite one another in a reversible commutator motor for electric hand tools, which device comprises a carrier for the brush holders rotatable concentrically around the motor shaft in addition to a stationary contact plate connected to each field coil.
With reversible motors for hand tools, for example rotary drills, use is often made of pairs of brushes located diametrically opposite one another which are rotated at a determined angle relative to the commutator in order to reverse the rotational direction of the electromotor. The design solutions known to date display a large number of parts which prevents a simple and therefore wholly or partially automated production method.
The object of the invention is to provide a design solution whereby the number of components is reduced to a minimum.
The device according to the invention is distinguished in that the contact plate is provided with two mutually separated contact strips, each provided with a plug and socket connection for the field coil contact whereby in each case the annular brush carrier displays a chamber open on one side for the accommodation of a brush carrier with brush, which open side is to be brought into contact with one of the contact strips.
The invention makes use of the possibility of using the brush not only in sliding contact with the commutator but also of using the brush carrier in sliding contact with the contact strips in the contact plate. Because the position of the brushes relative to the commutator has to be changed for reversing of the motor, use is also made of the possibility of switching over from the one contact strip to the other contact strip, which can take place simply with the surface of the brush carrier situated in the open side of the chamber. As a result the number of components in such a reversing device is considerably reduced.
The rotary connection between brush carrier and contact plate can be effected in a simple manner according to the invention through the use of a bayonet closure.
The operation of the rotatable brush carrier is simply achieved by providing the brush carrier with a hand grip which extends outside the motor housing so that it is accessible for the user.
In order to prevent the actuation of the reversing device while the motor is running a locking device is employed according to the invention which co-acts with the on-off switch of the motor power supply. This locking device is preferably operated according to the invention by the brush carrier or the brush chamber integrally arranged therein.